I included Distress Markers into this because they are part of my collection and they technically have the brush tip but it's seem pretty clear to me that they weren't intended to be used for lettering. In the video below, you can probably see that the elasticity of the nib is affected just with the amount of writing I did on that piece of paper.

So while I don't recommend you purchasing them for lettering - they are AWESOME for watercolor (in addition to their counterparts, Distress Ink pads). I often use these by scribbling some color out onto an acrylic block (or a Tombow Blending Palette) and then picking up the pigment with a water brush to achieve the watercolor lettering look.